v0.7.2

Patch: PR-receipt refs are now written under refs/aireceipts/* instead of the generic
refs/receipts/*. The old namespace collided with other tools that also publish to
refs/receipts/<slug> (e.g. an attestation producer storing an in-toto receipt.json at
the same path). In a repo running both, the namespace was occupied by the other tool's
payloads, so CI pr-check fetched a foreign ref, failed its schemaVersion check, and
silently posted nothing — the auto-attach hook fired and pushed refs, yet no receipt ever
appeared. aireceipts now owns refs/aireceipts/* and never reads or writes
refs/receipts/*, so the two coexist; the push classifier still recognizes both namespaces
so a foreign receipt-ref push is never mis-counted as a branch commit (PR #204). No
migration: aireceipts had never written a refs/receipts/* ref. Hooks and CI on @latest
adopt the new namespace together on this release. Rendered receipt output is byte-identical
(goldens unchanged); the only user-visible surface change is the ref name in pr --help.